The objective of this study is to evaluate the safety of an oil-based depot preparation of interleukin (IL-2) as a means to generate high concentrations of this cytokine within primary renal tumors. Data suggests that resistance to intravenously administered IL-2 may represent a failure to generate sufficiently high concentrations for prolonged periods of time within tumors. It is hypothe-sized that a depot preparation of IL-2 delivered directly into the arterial blood supply of a local tumor may overcome this resistance.